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As the weather was relatively mild throughout whole study period, the toe and foot temperatures stayed at considerably high levels in the insulated winter boots. Only a subject with his own shoes experienced cold feet.

4.8.1 Questionnaire at the end of the day

During the day the workloads varied and for each type of job the workload was somewhat different. In average the test persons rated their exertion very light 23%, light 20 %, moderate 47 % and heavy 10 % of total work time. In average they were working outdoors 4-6 hours and the length of an average work period outdoors was 1-2 hours. In average the test persons had 2-4 breaks during the day and the length of an average break was 30-45 minutes. The duration of warm work was less than 15 minutes per day. The workers were not disturbed by cold or were disturbed just occasionally. The workers related the cold sensation in feet to the footwear material (1 subject) and sweating (1) and considered these days similar or warmer compared to usual cold season workdays.

The footwear were considered comfortable except by 1 worker - he had chosen a too big size. The problems with the footwear were difficulty to walk, limited mobility and poor fit (1 subject), limiting effect on work ability (2), cold feet (a subject using his own shoes) and sweaty feet (1). A person, who often had to climb up and down platforms, considered the boots to be too heavy. Generally the boots were considered good and some workers were eager to get similar footwear. Two workers mentioned the boots to be “very good safety boots”. No subject had problem with slipping.

4.8.2 Foot skin temperatures

The foot skin temperature over time are shown in Figures 12 and 13. The foot skin temperatures stayed relatively high, usually over 30 °C. In subject 2 the foot skin temperature was somewhat lower already in the beginning. However, during the workday it raised higher than 30 °C. Enander et al (Enander et al., 1979) showed similar values for food processing workers in cold halls doing various

2 0 1 3 2 0 0 2 0 2 2 3 2 2 2 2 2 10 15 20 25 30 35 06:30 07:00 07:30 08:00 08:30 09:00 09:30 10:00 10:30 11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30 15:00 15:30 Time (hh:mm) Temperature (°C) -4 -3 -2 -1 0 1 2 3 4 Thermal sensation

Thermal sensation 3 Thermal sensation 4

Toe 3 Toe 4

Foot 3 Foot 4

Figure 12. Foot and toe temperatures of subjects 3 and 4 (fastening steel). Thick lines at time axis show work periods in the cold. Columns and numbers show the thermal sensa- tion in feet (1 - subject 3; 1 - subject 4) at given time point.

0 0 -1 -1 -1 -1 1 3 0 0 2 2 2 2 10 15 20 25 30 35 06:30 07:00 07:30 08:00 08:30 09:00 09:30 10:00 10:30 11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30 15:00 15:30 Time (hh:mm) Temperature (°C) -4 -3 -2 -1 0 1 2 3 4 Thermal sensation

Thermal sensation 7 Thermal sensation 8

Toe 7 Toe 8

Foot 7 Foot 8

Figure 13. Foot and toe temperatures of subjects 7 and 8 (signalling). Thick lines at time axis show work periods in the cold. Columns and numbers show the thermal sensation in feet (1 - subject 7; 1 - subject 8) at given time point.

jobs at 1 to 13 °C. The warm boots kept the foot skin temperature relatively con- stant for the whole workday. The thermal sensations of the feet (scale from +4 to -

4) were often warm or very warm. The exception was subject 7 who had his own shoes and during most of the day felt slightly cold in the feet. His foot skin tem- peratures stayed under 30 °C for most of the workday (Figure 13).

However, the toe temperatures varied more than the foot temperatures (Table 8). This could be related to the lower insulation of the toe zone (Paper III) and to the fact that the vasomotor activity is high in peripheral body parts. The lowest toe temperatures were occasionally between 17-18 °C. Commonly they stayed higher than 25 °C for most of the workday. In the beginning of the day most of the subjects had toe skin temperatures between 20-25 °C. It could depend on the preparation of the study, i.e. taping the sensors to the skin, while subjects were minimally dressed. Subjects 5 and 6 had the most stable toe temperatures if to exclude the start of the day. These subjects took off the footwear during the breaks and wore slippers instead. It is difficult, however, to say if the high and relatively stable toe temperature depended on that. The toe temperatures were in average 6 °C lower than foot skin temperatures. Toe temperature changes did not affect considerably thermal sensation of feet as has been shown before (Paper II; Tochihara et al., 1995). It could be related to that the skin temperatures stayed relatively high.

4.8.3 Sweat accumulation in footwear

The sweat accumulation in the footwear was at average 20 g per day and foot (range 10 - 30). Around 2 g of that stayed in the socks. The amount of sweat, that was accumulated in the footwear of subjects 5 and 6 (took off the footwear during breaks) did not differ from others. Sweating seems to affect footwear insulation depending on sweat rate, sweat amount, and probably also absorption capacity and evaporation resistance of the footwear. During sweating tests on a thermal foot model (Paper III) a considerable reduction of footwear insulation was shown. During those tests a sweat rate of 10 g/h was simulated. However, in everyday work situations the sweat accumulation is often not so high, in present study 1.4- 6.7 g/h/foot. At these sweat rates the insulation is reduced less, and this results in drier socks and thus more comfortable feet. However, even lower sweat rates (3 and 5 g/h/foot) have been shown to reduce footwear insulation considerably (Paper IV). It should be noted that in the field study some of the sweat did probably evaporate, and some weight gain could be related to the environment (dust, rain).